The presynaptic terminal of adrenergic neurons has a carrier that removes released norepinephrine (NE) from the synapse to terminate the nerve impulse. In addition to its role in neuronal transmission, the carrier system is the site of action of drugs such as cocaine, amphetamine and desmethylimipramine. Although the general properties of the carrier or uptake system have been described, details of the biochemistry of the carrier itself, such as its molecular nature, its concentration in the terminal membrane, and its interaction with ligands are not available. This project has developed an irreversible and specific inhibitor of NE uptake together with procedures that allow its selective interaction with the carrier. The synthesis of high specific activity tritium labeled precursor to inhibitor has also been accomplished so that the conditions and tools for a comprehensive biochemical study of the carrier system are now available. The work proposed will use labeled and unlabeled inhibitor, called ylamine, to isolate the carrier molecule, to study its turnover, and to determine the role of the carrier in the actions of sympathetic agents. The experiments will be conducted with tissues from rats and rabbits using biochemical separation procedures, in vitro pharmacological evaluation, and analytical chemical procedures. These studies will provide basic information on the action of antidepressants and drugs of abuse, as well as drugs used in the treatment of hypertension.